Norovirus is a virus that causes acute gastroenteritis such as vomiting and diarrhoea. Norovirus causes food poisoning from eating oysters and the like, and orally infects humans via feces or vomited material.
It is known that particles called as virus-like particles (VLPs) that resemble viral particles are formed when a baculovirus vector incorporated with the structural protein coding region of norovirus genome is expressed in insect cells. Though VLPs resemble viral particles in appearance, they do not contain virus genome and is not infectious.
Norovirus vaccine has been recently developed using VLPs as antigens and patent applications concerning it have been filed (Japanese Translation of PCT International Application Publication Nos. JP-T-2010-505766 and JP-T-2011-530295). In order to produce such norovirus vaccine, it is necessary to purify VLPs from the culture. As a purification method of VLPs of norovirus, there has been known a method disclosed in Patent Literature 1.
In Patent Literature 1, a method of purifying VLPs of norovirus using a multistep chromatographic process is disclosed (for example, claim 1), and as one example of the chromatography, chromatography using hydroxyapatite is listed (for example, claim 37). Further, Patent Literature 1 discloses that buffer containing phosphate at such high concentration as 10-1000 mM is used (for example, claim 59). In particular, it discloses that buffer containing phosphate at such high concentration as 100-200 mM is required to selectively elute VLPs from a hydroxyapatite support (for example, paragraph [0107]).